Is there a better way of writing a git pre-commit hook to check any php file in a commit for parse errors?

Question

What I have so far is

#!/bin/sh

php_syntax_check()
{
    retval=0
    for i in $(git-diff-index --name-only --cached HEAD -- | grep -e '\.php$'); do
        if [ -f $i ]; then
            output=$(php -l $i)
            retval=$?
            if [ $retval -gt 0 ]; then
                echo "=============================================================================="
                echo "Unstaging $i for the commit due to the follow parse errors"
                echo "$output"
                git reset -q HEAD $i
            fi
        fi
    done

    if [ $retval -gt 0 ]; then
        exit $retval
    fi
}
php_syntax_check

Answer 1

If the commit is a partial commit (not all the changes in the working tree are committed), then this make give incorrect results since it tests the working copy and not the staged copy.

One way to do this could be:

git diff --cached --name-only --diff-filter=ACMR | xargs git checkout-index --prefix=$TMPDIR/ --
find $TMPDIR -name '*.php' -print | xargs -n 1 php -l

Which would make a copy of the staged images into a scratch space and then run the test command on them there. If any of the files include other files in the build then you may have to recreate the whole staged image in the test tree and then test the changed files there (See: Git pre-commit hook : changed/added files).

Answer 2

I'm sorry if it's offtopic, but aren't you supposed to run some kind of automated tests (which would imply that the code has no syntax errors) before doing a commit?